1. Field
The aspects of the disclosed embodiments relate to the field of the control of airplane flights. More particularly, the aspects of the disclosed embodiments relate to devices intended to act on the drag force of planes generally grouped under the name of “airbrakes”.
2. Brief Description of Related Developments
The drag of airplanes is normally considered as a defect which must be fought since the drag is opposed to the forward motion of the airplane and increases the consumption of fuel.
However, there are particular times during the flight of a plane, when it is useful to increase the drag so as to decelerate more quickly than under the simple effect of the ordinary drag of the airplane or in order to avoid an excessive acceleration during a descent.
Being able to increase the drag at some times of the flight becomes all the more useful since maximum efforts are made by the design teams to reduce the cruise drag.
To increase the drag, an airplane 1 includes airbrakes 2, generally composed of rigid elements positioned so as not to generate drag during the cruise flight and including one or several so-called deployed positions, so that the rigid elements have a surface which opposes the forward motion in air. Many shapes of airbrakes, positioned on the wings of the airplane or on the fuselage, exist and are used on civil or military airplanes.
Such airbrakes are all the more efficient when the speed of the aircraft is high. More precisely, the drag force, thus the resulting deceleration, is directly a function of dynamic pressure, i.e. is, for a given position of the airbrakes, proportional to a term in ρv2 where ρ is the density of the fluid (air at the flight altitude) and V the displacement speed of the airplane with respect to the fluid.
The problem entailed in this braking means is the loss of efficiency when speed is reduced. It is, for example, 6 times lower at 50 m/s, which is the typical speed of a modern airplane at the time of the landing, than at 125 m/s, which is the typical speed at the end of the descent and it becomes negligible very rapidly when the speed is further reduced, more particularly after the landing.
Other means exist to slow down an airplane 1, more particularly after the landing, such as the reversal of the thrust direction of the motors 3 of the airplane or the braking of the wheels 4 in contact with the runway.
Although they are largely used on civil planes, such means have numerous defects.
Thrust inverters 5 used on reactors are complex, heavy and expensive to produce as well to exploit. In addition to the mass penalty they represent for the airplane, they reduce the performances of the motor in normal operation mode, because of the inevitable imperfections of such devices which induce aerodynamic drags and load losses which entail excessive consumptions.
Braking systems of the wheels 4 are of a limited efficiency, when the runway is contaminated by water, snow or ice and their utilization causes brakes and tires friction elements to wear and so these must be replaced all the more frequently when brakes are used intensively.
Then, there is a real interest in using means making it possible to obtain an efficient braking force of the airplane at any speed and which makes it possible to simplify the existing devices and to limit the use thereof in operation.